<style>
  * {
    padding: 0;
    margin: 0;
  }

body{
  height: 100vh;
  display: flex;
  background-color: #f5f5f5;
  flex-direction: column;
}
header{
  height: 40px;
  background-color: #3c3c3c;
}
main{
  flex: 1;
}
footer{
  height: 160px;
  background-color: #3c3c3c;
  display: flex;
  flex-direction: row;
  justify-content: space-between;
}
footer section {
  flex: 1;
  border-right: #227dc9 solid 10px;
}
</style>

<body>
  <header></header>
  <main> </main>
  <footer>
    <section></section>
    <section></section>
    <section></section>
  </footer>
</body>